Safety paper



Patented May '18, 1926.

ALFRED I. 'GONE, OF NEW YORK, N. SAFETY PAPER.

IlQo Drawing.

This invention relates to safety, papers of the class which areimpregnated with or carry various chemical substances intended to.produce color reactions when attempts are made to obliterate by chemicalmeans anything written or printed on the-surface of such .paper.

Numbers of such papers have hitherto been prepared and have generallybeen confined to providing means for detection when alterations havebeen attempted with the use of the ordinary devices of treating theWritten or printed characters on the paper .With eradicating fluids,composed of the 16 usual solutions of acids, alkalies, hypochlorite,hyposulphite, etc., but have been open to a' number of objections,especially, in that the skilled forger, knowing that he is dealing witha saftey paper, can take the pre- '2ocautions of avoiding-ofcounteracting the ordinary color react-lens hitherto employed as safetydevices.

The present invention, besides providing novel improvements asfto thematerials to be employed for the purpose of increased eficiency, alsoprovides means for frustrating attempts by'subsequent treatments toobliterate the effect of any primary reac tions produced whenalterations have been attempted, and also means for detection ofattempts to remove the chemicals from such safety aper before theapplication of eradicator uids, in order to avoid the tell-talediscolorations which would be produced by reactions with such chemicals,when present in the paper. The paper prepared as herein describeddevelops certain color' reactions with various chemicals, whereby anyattempt to eradicate a character produces unmistakable ocular evidenceof an attempt at falsification,'etc., and also provides means forshowing if an attempt has been made to wash out some of the chemicalmaterials from the I paper.

' bining with the paper certain salts of mercury, preferably insolublemercurous salts. I have found that insoluble mercurous salts in general.are adapted toafford a safety paper of the character described. I prefertouse the insoluble mercurous sulphanilate as the salt best adapted forthe purpose, and to this end I incorporate the mercurous sulphanilate inthe pulp before the latter is made into paper,

- Application filed May 6,

The invention consists essentially in com- 1925. Serial N0. 28,506.

Such mercurous salt, being insoluble, is obviously not so readily washedaway in the process of manufacturing the paper by the usual liquidsemployed for such purpose. Mercurous sulphanilate is also much lessliable to discolor the finished paper when exposed to the action oflight than when a paper is made with almost all other mercurous salts. Apaper thus made with, mercurous sulphanilate will develop with alkaliesa .brown or black color; with chlo-' rine or hypochlorites abrownish-red color develops; with thiosulphate (hyposulphite), sulphite,bisulphite, or ammonia, a brownish to black color will develop; if aniodide solution is applied to the paper in an attempt to wash out anycontained chemicals, the mercury sulphanilate will produce a yellow toblack discoloration.

In safety papers of the class described, it 1s always desirable toprovide for a multiplicity of side reactions so as to render itincreasingly diflicult to make alterations thereon without leaving someevidences of tampering, and the further measures necessary to make suchalterations will eventual- 1y render a document so unsightly as todefeat the object.

Although the mercurous sulphanilate itself affords a high degree ofprotection, I prefer to add certain other chemicals as an addedsafeguard. For this purpose I may also use sulphanilic acid or asulphanilate and/or benzidine sulphate. When these chemicals are usedthe benzidine sulphate, which is insoluble in water, as well as in theusual solvents, is incorporated in the pulp in conjunction with theinsoluble mercurous salt used, while the sulphanilate is applied to thefinished paper in the form of a size or impregnating solution.

The impregnating solution referred to is a solution of sulphanilic acidor, preferably, a more freely soluble salt thereof.

I have found that sulphanilic acid and its soluble salts afford a yellowstain reaction when applied to moistened unbleached or partly bleachedligno-cellulose paper, and I use this reaction as an added protectivemeasure so as to afford means to detect whether any attempt has beenmade to remove, by washing out the chemicals which have beenincorporated. Thus if a check, for instance, has been washed, and thesulphanilie constituent thus removed, this can eas- 10 ily bedemonstrated by the failure to afford a substantial characteristicyellow stain upon the moistened ligno-cellulose paper when the latter ispressed against the suspected document under invest-i ation.

The benzidine sulphate may also be optionally incorporated inconjunction with the mercurous salt, as an added measure of protection.Benzidine sulphate has been used in the manufacture of safety papers fora number of years. but while it affords a strong reaction withhypochlorite, yet, when used alone, the discoloration thus produced canbe readily removed, for instance, by treatment with asodiumhy'drosulphite solution.

However, when this well-known benzidine sulphate is incorporated in thepulp in combination with the mercurous salt as above disclosed, then theattem t to remove the benzidine stain will result in the development ofa black stain which is practically notremovable.

The various color reactions, together with the varied and numerousmanipulations that would be required for the removal of the stainsdeveloped by them will'render the document so unsightly, or impair itsappearance to such an extent, as to make it highly unsafe, for instance,to attempt to pass a check or other negotiable instrument made fromapaper prepared as herein described and so manipulated.

Any attempt to remove any of the color stains developed as abovedescribed will'result in either intensifying such color stain, orchanging that color stain to another, with the result that thepaperbecomes still more unsightly and dangerouseto pass.

If the paper survives the effort to remove the soluble and insolublechemicals, the absence of the reaction with the moistenedligno-cellulose paper mentioned above will in itself disclose the factthat the paper has been tampered with.

T he sulphanilate impregnation and the addition of the benzidinesulphate may be dispensed with without disturbing the protectionafforded by the insoluble mercurous salt incorporated in the pulp, butmanifestly the protection afforded is increased as additional agents areemployed, and it is therefore almost always desirable to incorporatethose mentioned and even others, ac-

cording to the degree and character of the protection desired. It ispreferable to incorporate about 2% of the insoluble mercuroussulphanilate in the pulp; of the sulphanilic acid or a soluble salt ofsulphanilic about 1% should be incorporated in order to afforddependable results; and of the benzidine sulphate about may beincorporated; but the materials can be used in varying quantitiesaccording to the in- Obviously also various other chemicals,

which will not react with those mentioned herein toimpair theirefficiency, may be added, optionally, to produce any further specialreaction as may be desired. It is not my desire to be limited to anyspecific combination of materials, as the invention is susceptible ofsome modifications, as indicated or otherwise apparent, all of whichwill come within the scope of the invention and without departing fromthe spirit thereof.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

11. A safety paper containing a mercurous sa t.

' 2. A safety papercontaining an insoluble mercurous salt.

3. A safety paper containing mercurous sulphanilate.

' 4'. A safety paper containing mercurous sulphanilate and sulphanilicacid or a soluble salt of sulphanilic acid.

5. A paper having incorporated therein mercurous sulphanilate andimpregnated with a solution of sulphanilic acid or a soluble salt ofsulphanilic acid.

6. The process of making a safetyl which consists of incorporating in tmercurous sulphanilate.

7. The process of making a safety paper which consists of impregnatingthe paper with mercurous sulphanilate and sulphanilic acid or a. solublesalt of sulphanilic acid.

8. The process of making a safety paper by incorporating in the pulpmercurous sulphanilate and impregnating the paper with sulphanilic aci'dora soluble salt of sulphanilic acid.

9. A safety paper containing an insoluble mercurous salt and asulphanilate.

10. A safety paper containing benzidine sulphate in conjunction with aninsoluble mercurous salt.

11. A safety paper containing benzidine sulphate in conjunction withmercurous sulphanilate.

12. A safety paper containing a substantially insoluble mercurous salt,sulphanilic acid or a salt theerof, and benzidine sulphate.

13. A safety paper containing mercurous sulphanilate, sulphanilic acidor a salt thereof, and benzidine sulphate.

ALFRED I. CONE.

paper e pulp Ill

